JP6322039B2 - Control device for variable capacity turbocharger - Google Patents

Description

  The present invention relates to a control device for a variable displacement turbocharger.

  Conventionally, as described in, for example, Patent Document 1, a variable capacity turbocharger that can change the flow rate of exhaust gas flowing into a turbine is known as a turbocharger provided in an engine. In the variable displacement turbocharger of Patent Document 1, a target value for the supercharging pressure is set based on the operating state of the engine, and the opening of the variable nozzle is controlled so as to be the set target value. Specifically, the target boost pressure set based on the engine speed and the fuel injection amount is compared with the actual boost pressure acquired by the sensor, and the variable nozzle is set according to the comparison result. The opening is controlled.

Japanese Patent Laid-Open No. 10-331648

  By the way, in the turbocharger, when an excessive rotation of the turbine rotation speed that is the rotation speed of the turbocharger occurs, the mechanical load on the components of the turbocharger increases.

  An object of the present invention is to provide a control device for a variable capacity turbocharger that can suppress over-rotation of the turbocharger.

  The variable capacity turbocharger control device that solves the above problems repeatedly sets the target pressure of the exhaust pressure, which is the pressure in the exhaust manifold, and controls the opening of the variable nozzle so that the exhaust pressure becomes the target pressure. A basic pressure calculating unit that calculates a basic pressure that is a candidate for the target pressure based on information related to an operating state of the engine, and a limiting pressure that is a candidate for the target pressure is related to the operating state of the turbocharger. A limiting pressure calculation unit that calculates based on the turbine rotational speed as information, and the limiting pressure calculation unit includes expansion ratio data in which an expansion ratio in the turbine is defined in advance for each turbine rotational speed, The expansion ratio defined by the turbine speed is selected from the expansion ratio data, and the selected expansion ratio is adjusted to the turbine. In the expansion ratio data, the expansion ratio is lower as the turbine rotational speed is higher in the range where the turbine rotational speed is larger than the allowable rotational speed. The basic pressure is set to the target pressure when the basic pressure is less than or equal to the limiting pressure, and the limiting pressure is set to the target pressure when the basic pressure is higher than the limiting pressure.

  According to the above configuration, when the basic pressure is higher than the limit pressure, the limit pressure is set as the target pressure. Thereby, the energy given to a turbine is restrict | limited and the raise of turbine rotation speed is suppressed. As a result, excessive rotation of the turbocharger can be suppressed.

  In the variable capacity turbocharger control device, the expansion ratio data includes a reference expansion ratio associated with a reference atmospheric pressure, which is an atmospheric pressure used as a reference when selecting the expansion ratio, and the reference atmospheric pressure. The low-pressure expansion ratio associated with a low atmospheric pressure, the low-pressure expansion ratio being a value smaller than the reference expansion ratio is defined in advance for each turbine speed, and the limiting pressure calculation unit is It is preferable that the expansion ratio corresponding to the turbine speed and the atmospheric pressure is selected from the expansion ratio data.

  The density of air becomes lower as the atmospheric pressure is lower. Therefore, in the turbocharger, the turbine rotation speed is likely to increase as the atmospheric pressure is lower. According to the above configuration, it is possible to reduce the limit pressure when the turbine rotation speed is likely to increase due to atmospheric pressure. That is, it is possible to change the limit pressure according to the ease of increasing the turbine rotational speed.

In the control apparatus for a variable displacement turbocharger, the expansion ratio data includes a plurality of data in which one expansion ratio is defined for each turbine rotation speed, and the reference atmospheric pressure has a predetermined range. The plurality of data correspond to reference data corresponding to the reference atmospheric pressure, low pressure data corresponding to an atmospheric pressure lower than the reference atmospheric pressure, and atmospheric pressure higher than the reference atmospheric pressure. High pressure data.
According to the above configuration, since the expansion ratio data is composed of three data according to the atmospheric pressure, the configuration of the expansion ratio data can be simplified while enabling the setting of the expansion ratio according to the atmospheric pressure.

  In the control apparatus for a variable displacement turbocharger, the limiting pressure calculation unit is a first limiting pressure calculation unit, the limiting pressure is a first limiting pressure, and the expansion ratio data is first expansion ratio data, The expansion ratio selected from the first expansion ratio data is a first expansion ratio, and a second limit pressure that is a candidate for the target pressure is determined based on an intake air amount that is information related to the operating state of the turbocharger. A second limiting pressure calculating unit for calculating, wherein the second limiting pressure calculating unit includes second expansion ratio data in which the expansion ratio is defined in advance for each intake air amount; Selecting the specified expansion ratio as the second expansion ratio from the second expansion ratio data, multiplying the selected second expansion ratio by the turbine outlet pressure to calculate the second limit pressure; Said Control unit, the base pressure, the first limit pressure, and it is preferable to set the smallest value among the second limit pressure to the target pressure.

  According to the said structure, the energy provided to a turbine according to the amount of intake air can be restrict | limited. As a result, surging that tends to occur when the amount of intake air is small and the pressure ratio in the compressor is large can be suppressed.

In the variable displacement turbocharger control device, the second expansion ratio data is a second reference expansion associated with a second reference atmospheric pressure, which is an atmospheric pressure used as a reference when selecting the second expansion ratio. the ratio, a second low-pressure expansion ratio associated with a lower atmospheric pressure than the second reference atmospheric pressure, and said second low-pressure expansion ratio is smaller than the second reference expansion ratio, the Preferably, each intake air amount is defined in advance, and the second limit pressure calculation unit selects the second expansion ratio corresponding to the current intake air amount and the atmospheric pressure from the second expansion ratio data. .

  According to the above configuration, when the atmospheric pressure is lower than the reference atmospheric pressure, that is, when the turbine rotation speed tends to increase and the pressure ratio in the compressor tends to increase, the second low-pressure expansion ratio lower than the second reference expansion ratio is used. Thus, the second limit pressure is calculated. As a result, surging is further suppressed.

It is a schematic block diagram which shows schematic structure of the engine by which one Embodiment of the control apparatus of a variable displacement type turbocharger is mounted. It is a block diagram which shows the structure of the control apparatus of a variable capacity type turbocharger. It is a calculation block diagram of target pressure. It is a graph which shows typically data which constitutes the 1st expansion ratio data, (a) is a graph which shows the 1st standard data, (b) is a graph which shows the 1st low pressure data, (c) is the 1st high pressure data It is a graph which shows. It is a graph which shows typically the data which constitute the 2nd expansion ratio data, (a) is a graph which shows the 2nd standard data, (b) is a graph which shows the 2nd low pressure data, (c) is the 2nd high pressure data It is a graph which shows.

  With reference to FIGS. 1 to 5, an embodiment embodying a control device for a variable capacity turbocharger will be described. First, the overall configuration of a diesel engine equipped with a variable capacity turbocharger will be described with reference to FIG.

[Diesel engine 10]
As shown in FIG. 1, a cylinder block 11 of a diesel engine 10 (hereinafter referred to as the engine 10) has four cylinders 12 arranged in a row. Fuel is injected into each cylinder 12 from an injector 13. Connected to the cylinder block 11 are an intake manifold 14 for supplying intake air to each cylinder 12 and an exhaust manifold 15 into which exhaust gas from each cylinder 12 flows.

  An air cleaner, a compressor 18 of a turbocharger 17 and an intercooler 19 (not shown) are attached to the intake passage 16 connected to the intake manifold 14 from the upstream side.

  On the other hand, a turbine 22 connected to the above-described compressor 18 via a connecting shaft 21 is attached to the exhaust passage 20 connected to the exhaust manifold 15. Connected to the exhaust manifold 15 is an EGR passage 25 that is connected to the intake passage 16 and introduces part of the exhaust gas into the intake passage 16.

  An EGR cooler 26 is attached to the EGR passage 25. On the downstream side of the EGR cooler 26, an EGR valve 27 capable of changing the flow path cross-sectional area of the EGR passage 25 is attached. The opening degree of the EGR valve 27 is controlled by an EGR control device (not shown). A part of the exhaust gas is introduced into the intake passage 16 through the EGR passage 25 when the EGR valve 27 is in the open state, and the working gas which is a mixed gas of the exhaust gas and the intake air is supplied to the cylinder 12. The Hereinafter, the exhaust gas flowing through the EGR passage 25 is referred to as EGR gas.

  The turbocharger 17 composed of the compressor 18 and the turbine 22 is a variable capacity turbocharger (VNT: Variable Nozzle Turbo) in which a variable nozzle 28 is disposed in the turbine 22. The variable nozzle 28 adjusts the exhaust pressure that is the pressure in the exhaust manifold 15 and the amount of exhaust gas flowing into the turbine 22 by changing the opening degree by driving an actuator 29 having a stepping motor. The opening degree of the variable nozzle 28 is controlled by a VNT control device 50 that is a control device for a variable displacement turbocharger.

  The engine 10 is provided with various sensors that detect information related to at least one of the operating state of the engine 10 and the operating state of the turbocharger 17 and output a signal indicating the detected value to the VNT control device 50. For example, an EGR pressure sensor 31 and an EGR temperature sensor 34 are attached to the EGR passage 25 downstream of the EGR cooler 26 and upstream of the EGR valve 27. The EGR pressure sensor 31 detects an EGR pressure Pegr that is the pressure of the EGR gas flowing into the EGR valve 27. The EGR temperature sensor 34 detects an EGR temperature Teg that is the temperature of the EGR gas flowing into the EGR valve 27.

  A boost pressure sensor 32 that detects the boost pressure Pb that is the pressure of the working gas is attached to the intake passage 16 downstream of the connection portion between the intake passage 16 and the EGR passage 25. An intake air amount sensor 36 that detects an intake air amount Qa that is a volume flow rate of the intake air flowing through the intake passage 16 is attached to the intake passage 16 upstream of the compressor 18. An intake air temperature sensor 35 that detects an intake air temperature Tin that is the temperature of the working gas immediately before flowing into the cylinder 12 is attached to the intake manifold 14.

  The engine 10 includes an engine speed sensor 37 that detects an engine speed Ne that is the speed of the crankshaft 24 and a turbine speed that detects a turbine speed Nt that is the speed of the connecting shaft 21 of the turbocharger 17. A number sensor 38 is provided.

[VNT control device 50]
The configuration of the VNT control device 50 will be described with reference to FIGS.
As shown in FIG. 2, the control unit 51 of the VNT control device 50 includes a CPU, a ROM, a RAM, and the like. The acquisition unit 52 acquires an external signal, and the calculation unit 53 performs various calculations. A storage unit 54 that stores various control programs and various data, and a nozzle drive unit 55 that drives the actuator 29 are provided. The control unit 51 executes the driving process of the variable nozzle 28 using the signal acquired by the acquisition unit 52 and the various data stored in the storage unit 54 according to various control programs stored in the storage unit 54.

  The acquisition unit 52 acquires the EGR pressure Pegr, the boost pressure Pb, the EGR temperature Teg, the intake air temperature Tin, the intake air amount Qa, the turbine speed Nt, and the engine speed Ne based on the signals output from the various sensors described above. . The acquisition unit 52 acquires the fuel injection amount Qf from the fuel injection control unit 39 that controls the fuel injection amount, and detects the opening degree of the EGR valve 27 from the EGR valve opening degree sensor 40 based on the opening degree of the EGR valve 27. A certain EGR valve opening VTegr is acquired. The acquisition unit 52 acquires the nozzle opening VTa that is the opening of the variable nozzle 28 from the variable nozzle opening sensor 41 that detects the opening of the variable nozzle 28. The acquisition unit 52 acquires the atmospheric pressure Patm that is the pressure value of the atmospheric pressure from the atmospheric pressure sensor 42 that detects the atmospheric pressure.

  The calculation unit 53 calculates a target opening area At that is a target value of the opening area of the variable nozzle 28 using various detection values acquired by the acquisition unit 52. The calculation unit 53 calculates the target nozzle opening VTt that embodies the target opening area At, and the opening required to change the opening of the variable nozzle 28 from the nozzle opening VTa to the target nozzle opening VTt. The indicated opening degree VTc is calculated. The calculating unit 53 outputs the calculated instruction opening VTc to the nozzle driving unit 55.

  The nozzle drive unit 55 generates a drive signal for changing the opening of the variable nozzle 28 by the indicated opening VTc input from the calculation unit 53, and outputs the generated drive signal to the actuator 29.

Ｇ ：タービン２２に流入する排気ガスの質量流量である流入量Ｇｔｉ
Ｐ１：エキゾーストマニホールド１５内の排気ガスの圧力である排気圧力Ｐｅｍの目標圧力Ｐｅｍｔ
Ｐ２：タービン２２の出口における排気ガスの圧力である出口圧力Ｐｔｅ
Ｔ１：タービンに流入する排気ガスの温度である流入温度Ｔｔｉ
Ａ ：可変ノズル２８の目標開口面積Ａｔ Hereinafter, various values calculated by the calculation unit 53 and an example of the calculation method will be described. In the following, κ is the specific heat ratio of the exhaust gas, and R is the gas constant.
[Target opening area At]
The computing unit 53 computes the target opening area At of the variable nozzle 28 by applying the following value to Equation (1) based on Bernoulli's theorem.

G: Inflow amount Gti which is a mass flow rate of the exhaust gas flowing into the turbine 22
P1: Target pressure Pemt of the exhaust pressure Pem, which is the pressure of the exhaust gas in the exhaust manifold 15
P2: outlet pressure Pte which is the pressure of the exhaust gas at the outlet of the turbine 22
T1: Inflow temperature Tti which is the temperature of the exhaust gas flowing into the turbine
A: Target opening area At of the variable nozzle 28

[Working gas amount Gwg]
The calculation unit 53 calculates a working gas amount Gwg that is a mass flow rate of the working gas supplied to the cylinder 12. The computing unit 53 computes the working gas amount Gwg by substituting the following values for the state equation P × V = Gwg × R × T.
P: Intake pressure Pwg
V: Multiplication value of engine speed Ne and displacement D of engine 10 T: Intake air temperature Tin

[EGR amount Geg]
The calculation unit 53 calculates the EGR amount Geg, which is the mass flow rate of the EGR gas, by applying detection values from various sensors to the above equation (1).
G: EGR amount Geg
P1: EGR pressure Pegr
P2: Boost pressure Pb
T1: EGR temperature Teg
A: Opening area Aeg of the EGR valve 27 based on the EGR valve opening VTegr

[EGR rate η]
The calculator 53 calculates the EGR rate η (= Geg / Gwg) by dividing the EGR amount Geg by the working gas amount Gwg.

[Exhaust pressure Pem]
The calculation unit 53 calculates the exhaust pressure Pem based on the EGR passage data 56 stored in the storage unit 54. The EGR passage data 56 is data in which the pressure loss value ΔPegr of EGR gas between the inlet of the EGR passage 25 and the EGR pressure sensor 31 is defined for each EGR amount Geg. The calculation unit 53 reads the pressure loss value ΔPegr corresponding to the EGR amount Geg from the EGR passage data 56, and calculates the exhaust pressure Pem by adding the read pressure loss value to the EGR pressure Pegr.

[Inflow temperature Tti]
The calculation unit 53 calculates the inflow temperature Tti based on the working gas amount Gwg, the EGR rate η, the fuel injection amount Qf that is an input value from the fuel injection control unit 39, and the temperature data 57 stored in the storage unit 54. To do. At this time, the temperature data 57 is data in which the temperature of the exhaust gas is uniquely defined using the working gas amount Gwg, the EGR rate η, and the fuel injection amount Qf as parameters. And the calculating part 53 calculates the inflow temperature Tti by reading the temperature according to the working gas amount Gwg, the EGR rate η, and the fuel injection amount Qf from the temperature data 57.

[Inflow Gti]
The calculator 53 calculates an inflow amount Gti that is a mass flow rate of the exhaust gas flowing into the turbine 22. The calculation unit 53 calculates the exhaust gas inflow amount Gti (= Gwg−Geg) by subtracting the EGR amount Geg from the working gas amount Gwg.

[Outlet pressure Pte]
The calculation unit 53 calculates the outlet pressure Pte based on the inflow amount Gti, the atmospheric pressure Patm that is a detection value of the atmospheric pressure sensor 42, and the exhaust passage data 58 stored in the storage unit 54. The exhaust passage data 58 indicates that the pressure loss value ΔPep generated in the exhaust gas from the outlet of the turbine 22 to the atmosphere is a volume flow rate based on the inflow amount Gti to the turbine 22 Gti × (Tti ^ 1 / 2) Data defined for each / Pem. The calculator 53 reads the pressure loss value ΔPep corresponding to the inflow amount Gti from the exhaust passage data 58, and calculates the outlet pressure Pte by adding the read pressure loss value ΔPep to the atmospheric pressure Patm.

[Target pressure Pemt]
As shown in FIG. 3, the calculation unit 53 calculates a target pressure Pemt of the exhaust pressure Pem. The calculation unit 53 calculates a basic pressure PemS that is a target pressure based on the operating state of the engine 10 and a first limit that calculates a first limit pressure Pem1 that is a target pressure based on the turbine speed Nt. A pressure calculation unit 60 and a second limit pressure calculation unit 61 that calculates a second limit pressure Pem2 that is a target pressure based on the intake air amount Qa are provided. Further, the calculation unit 53 includes a target pressure selection unit 63 that selects the smallest value among the basic pressure PemS, the first limit pressure Pem1, and the second limit pressure Pem2 as the target pressure Pemt.

  The basic pressure calculation unit 59 calculates the basic pressure PemS based on the engine speed Ne and the fuel injection amount Qf. The basic pressure PemS is an exhaust pressure Pem that embodies a boost pressure suitable for the engine speed Ne and the fuel injection amount Qf.

  The first limit pressure calculation unit 60 calculates a first expansion ratio π1 that is an expansion ratio in the turbine 22 and a first multiplication that multiplies the first expansion ratio π1 by the outlet pressure Pte. Part 65. The first expansion ratio calculation unit 64 calculates the first expansion ratio π1 based on the turbine rotation speed Nt, the atmospheric pressure Patm, the first expansion ratio data 66 stored in the storage unit 54, and these. The first multiplication unit 65 outputs the multiplication result of the first expansion ratio π1 and the outlet pressure Pte to the target pressure selection unit 63 as the first limit pressure Pem1.

  The second limit pressure calculating unit 61 calculates a second expansion ratio π2 that is an expansion ratio in the turbine 22, and a second multiplication that multiplies the second expansion ratio π2 by the outlet pressure Pte. Part 68. The second expansion ratio calculator 67 calculates the second expansion ratio π2 based on the intake air amount Qa, the atmospheric pressure Patm, the second expansion ratio data 69 stored in the storage unit 54, and these. The second multiplication unit 68 outputs the multiplication result of the second expansion ratio π2 and the outlet pressure Pte to the target pressure selection unit 63 as the second limit pressure Pem2.

[First expansion ratio data 66]
As shown in FIG. 4, the first expansion ratio data 66 includes a first expansion ratio π1 that is an expansion ratio that suppresses excessive turbocharger rotation for each turbine speed Nt based on the results of experiments and simulations performed in advance. Is stipulated. The first expansion ratio data 66 includes three data corresponding to the atmospheric pressure Patm, first reference data 70, first low pressure data 71, and first high pressure data 72.

  As shown in FIG. 4A, the first reference data 70 is data that is selected when the atmospheric pressure Patm is included in the predetermined first reference range, and the first reference data 70 is included in each turbine rotational speed Nt. An expansion ratio π1S is defined. In the first reference expansion ratio π1S, a maximum expansion ratio πmax is defined in a range equal to or lower than the reference rotational speed Nt1, and a value that is lower as the turbine rotational speed Nt is higher is defined in a range higher than the reference rotational speed Nt1.

  When the atmospheric pressure Patm is included in the reference range, normally, even if the operating state of the engine 10 is in a transient state, the turbine rotational speed Nt changes within the reference rotational speed Nt1 or less, and the expansion ratio is It changes at a value below the maximum expansion ratio πmax.

  As shown in FIG. 4B, the first low-pressure data 71 is data that is selected when the atmospheric pressure Patm is lower than the first reference range, and the first low-pressure expansion is set for each turbine speed Nt. A ratio π1L is defined. In the first low pressure expansion ratio π1L, a maximum expansion ratio πmax is defined in a range not higher than the low pressure rotation speed Nt2 lower than the reference rotation speed Nt1, and in a range higher than the low pressure rotation speed Nt2, the first reference expansion ratio π1S. And a value that decreases as the turbine speed Nt increases.

  As shown in FIG. 4C, the first high-pressure data 72 is data selected when the atmospheric pressure Patm is higher than the first reference range, and the first high-pressure expansion is set for each turbine speed Nt. The ratio π1H is specified. The first high-pressure expansion ratio π1H has a maximum expansion ratio πmax defined in a range not higher than the high-speed rotation speed Nt3 higher than the reference rotation speed Nt1, and higher than the first reference expansion ratio π1S in a range higher than the high-pressure rotation speed Nt3. A value that is high and decreases as the turbine speed Nt increases is defined.

  The high-speed rotation speed Nt3 is set to a turbine rotation speed Nt that is equal to or lower than the allowable rotation speed of the turbine 22. That is, the first expansion ratio π1 defined in the first expansion ratio data 66 has a lower value as the turbine rotational speed Nt is higher in a range where the turbine rotational speed Nt is higher than the allowable rotational speed if the atmospheric pressure is the same. . Further, the allowable rotational speed may be a value slightly lower than the turbine rotational speed at which the turbocharger is determined to be excessively rotated, or may be the turbine rotational speed itself at which the turbocharger is determined to be excessively rotated.

  Regarding the first reference data 70, the reference rotation speed Nt1 and the first reference expansion ratio π1S at the turbine rotation speed Nt higher than the reference rotation speed Nt1 are based on the peripheral speed of the compressor 18 and the peripheral speed of the turbine 22, for example. Are preferably defined. The same applies to the first low pressure data 71 and the first high pressure data 72.

[Second expansion ratio data 69]
Here, in the turbocharger, surging may occur in which the compressor 18 idles. During the period in which surging occurs, even if the compressor 18 rotates, the intake air is not supercharged, and the intake air may flow backward. Further, vibration may occur in the turbocharger 17. Therefore, when surging occurs, the mechanical load on the components of the turbocharger increases.

  Surging is likely to occur when the intake air amount Qa is small and the pressure ratio, which is the ratio between the outlet pressure of the compressor 18 and the inlet pressure of the compressor 18, is high. Further, since the pressure ratio tends to increase as the energy applied to the turbine 22 increases, surging is more likely to occur as the expansion ratio in the turbine 22 increases.

  As shown in FIG. 5, the second expansion ratio data 69 is data in which a second expansion ratio π2, which is an expansion ratio that suppresses surging for each intake air amount Qa, is defined based on the results of experiments and simulations performed in advance. It is. The second expansion ratio data 69 includes three data corresponding to the atmospheric pressure Patm, second reference data 73, second low pressure data 74, and second high pressure data 75.

  As shown in FIG. 5A, the second reference data 73 is data selected when the atmospheric pressure Patm is included in the predetermined second reference range, and the second reference expansion is included in each intake air amount Qa. The ratio π2S is specified. In the second reference expansion ratio π2S, a minimum expansion ratio πmin is defined in the range of the intake air amount Qa1L or less. The higher the intake air amount Qa in the range of the intake air amount Qa1H or less, the higher the intake air amount Qa. A high value is specified. In the second reference expansion ratio π2S, the maximum expansion ratio πmax is defined in a range higher than the intake air amount Qa1H.

  As shown in FIG. 5B, the second low-pressure data 74 is data selected when the atmospheric pressure Patm is lower than the second reference range, and the second low-pressure expansion ratio for each intake air amount Qa. π2L is defined. In the second low-pressure expansion ratio π2L, a minimum expansion ratio πmin is defined in the range of the intake air amount Qa2L which is higher than the intake air amount Qa1L. The second low-pressure expansion ratio π2L is lower than the second reference expansion ratio π2S in the range of the intake air amount Qa2H that is higher than the intake air amount Qa2L and higher than the intake air amount Qa1H, and the intake air amount. A value that increases as Qa increases is defined. In the second low pressure expansion ratio π2L, the maximum expansion ratio πmax is defined in a range higher than the intake air amount Qa2H.

  As shown in FIG. 5C, the second high-pressure data 75 is data selected when the atmospheric pressure Patm is higher than the second reference range, and the second high-pressure expansion ratio for each intake air amount Qa. π2H is specified. In the second high-pressure expansion ratio π2H, a minimum expansion ratio πmin is defined in the range of the intake air amount Qa3L that is lower than the intake air amount Qa1L. The second high-pressure expansion ratio π2H is higher than the second reference expansion ratio π2S in the range of the intake air amount Qa3H that is higher than the intake air amount Qa3L and lower than the intake air amount Qa1H, and the intake air amount. A value that increases as Qa increases is defined.

[Action]
Next, the operation of the VNT control device 50 described above will be described. The VNT control device 50 controls the opening degree of the variable nozzle 28 so that the exhaust pressure Pem becomes the target pressure Pemt. The target pressure Pemt includes a basic pressure PemS based on the engine speed Ne and the fuel injection amount Qf, a first limit pressure Pem1 that suppresses excessive rotation of the turbocharger 17, and a second limit pressure Pem2 that suppresses surging of the turbocharger 17. Is the smallest value of.

  That is, the target pressure Pemt is a value that is less than or equal to the first limit pressure Pem1 and less than or equal to the second limit pressure Pem2, and is a pressure that can suppress over-rotation and surging of the turbocharger 17. Therefore, for example, when the basic pressure PemS is selected as the target pressure Pemt, the exhaust pressure Pem suitable for the engine speed Ne and the fuel injection amount Qf is realized while suppressing the excessive rotation and surging of the turbocharger 17. .

According to the VNT control apparatus 50 of the said embodiment, the effect shown below is acquired.
(1) Since the target pressure Pemt is set to be equal to or lower than the first limit pressure Pem1, excessive rotation of the turbocharger 17 is suppressed.

  (2) The range higher than the permissible rotational speed is defined as the first expansion ratio π1 having a value that decreases as the turbine rotational speed Nt increases. As a result, excessive rotation of the turbocharger 17 is further suppressed.

  (3) Since the air density is low when the atmospheric pressure Patm is low, the resistance of the air to the rotation of the compressor 18 is small, and the turbine speed Nt tends to increase. In this regard, according to the above configuration, the first expansion ratio data 66 defines a plurality of first expansion ratios π1 corresponding to the atmospheric pressure Patm for one turbine speed Nt. As a result, the excessive rotation of the turbocharger 17 is further suppressed by selecting the first expansion ratio π1 corresponding to the atmospheric pressure Patm.

  (4) The first expansion ratio data 66 includes three data corresponding to the atmospheric pressure, first reference data 70, first low pressure data 71, and first high pressure data 72. Thus, the configuration of the first expansion ratio data 66 and the calculation by the calculation unit 53 can be simplified while realizing the selection of the first expansion ratio π1 according to the atmospheric pressure Patm.

(5) Since the target pressure Pemt is set to be equal to or lower than the second limit pressure Pem2, surging of the turbocharger 17 is suppressed.
(6) When the atmospheric pressure Patm is low, the turbine speed Nt tends to increase. That is, the pressure ratio tends to be higher as the atmospheric pressure Patm is lower. In this regard, according to the above configuration, the second expansion ratio data 69 defines a plurality of second expansion ratios π2 corresponding to the atmospheric pressure Patm for one intake air amount Qa. As a result, the surcharge of the turbocharger is further suppressed by selecting the second expansion ratio π2 corresponding to the atmospheric pressure Patm.

  (7) The second expansion ratio data 69 includes three data corresponding to the atmospheric pressure, second reference data 73, second low pressure data 74, and second high pressure data 75. Thus, the configuration of the second expansion ratio data 69 and the calculation by the calculation unit 53 can be simplified while realizing the selection of the second expansion ratio π2 according to the atmospheric pressure Patm.

In addition, the said embodiment can also be suitably changed and implemented as follows.
The calculation unit 53 selects a small value from the first expansion ratio π1 and the second expansion ratio π2, and outputs a value obtained by multiplying the selected expansion ratio by the outlet pressure Pte to the target pressure selection unit 63. May be. According to such a configuration, the number of multiplications of the outlet pressure Pte with respect to the expansion ratio is smaller than in the above embodiment, and the calculation by the calculation unit 53 can be further simplified.

  The second expansion ratio data 69 may be data in which one second expansion ratio π2 is defined for one intake air amount Qa regardless of the atmospheric pressure Patm. According to this, the configuration of the second expansion ratio data 69 and the calculation by the calculation unit 53 can be further simplified.

  When the second expansion ratio data 69 is composed of a plurality of data, the plurality of data may be four or more data corresponding to the atmospheric pressure Patm. According to this configuration, the accuracy of the second limit pressure Pem2 corresponding to the atmospheric pressure Patm is increased.

  The calculation unit 53 may have a configuration in which the second limit pressure calculation unit 61 is omitted in order to suppress excessive rotation of the turbocharger. That is, the calculation unit 53 may be configured to select a smaller value of the basic pressure PemS and the first limit pressure Pem1 as the target pressure Pemt.

  The first expansion ratio data 66 may be data in which one first expansion ratio π1 is defined for one turbine rotational speed Nt regardless of the atmospheric pressure Patm. According to such a configuration, the configuration of the first expansion ratio data 66 and the calculation by the calculation unit 53 can be further simplified.

  When the first expansion ratio data 66 includes a plurality of data, the plurality of data may be four or more data corresponding to the atmospheric pressure Patm. According to this configuration, the accuracy of the first limit pressure Pem1 corresponding to the atmospheric pressure Patm is increased.

The first reference range and the second reference range may be the same range or different ranges.
The basic pressure PemS is not limited to that calculated based on the engine speed Ne and the fuel injection amount Qf. The basic pressure PemS may be calculated based on information selected from information related to the operating state of the engine 10, for example, based on the engine speed Ne, the fuel injection amount Qf, the accelerator opening ACC, the intake pressure Pwg, and the like. It may be calculated.

The outlet pressure Pte may be a detection value of an outlet pressure sensor that detects the outlet pressure Pte. According to such a configuration, the accuracy of the first limit pressure Pem1 and the second limit pressure Pem2 is increased.
The fuel injection control unit that controls the fuel injection amount Qf and the VNT control device 50 may be incorporated in the same control device.

  DESCRIPTION OF SYMBOLS 17 ... Turbocharger, 18 ... Compressor, 21 ... Connecting shaft, 22 ... Turbine, 28 ... Variable nozzle, 29 ... Actuator, 41 ... Variable nozzle opening sensor, 42 ... Atmospheric pressure sensor, 50 ... VNT controller, 51 ... Control , 52 ... acquisition unit, 53 ... calculation unit, 54 ... storage unit, 55 ... nozzle drive unit, 56 ... EGR passage data, 57 ... temperature data, 58 ... exhaust passage data, 59 ... basic pressure computation unit, 60 ... first DESCRIPTION OF SYMBOLS 1 Limit pressure calculating part, 61 ... 2nd limit pressure calculating part, 63 ... Target pressure selecting part, 64 ... 1st expansion ratio calculating part, 65 ... 1st multiplication part, 66 ... 1st expansion ratio data, 67 ... 2nd Expansion ratio calculation unit, 68 ... second multiplication unit, 69 ... second expansion ratio data, 70 ... first reference data, 71 ... first low pressure data, 72 ... first high pressure data, 73 ... second reference data, 74 ... Second low pressure de Data, 75 ... the second high-pressure data.

Claims (5)

A control unit that repeatedly sets the target pressure of the exhaust pressure, which is the pressure in the exhaust manifold, and controls the opening of the variable nozzle so that the exhaust pressure becomes the target pressure;
A basic pressure calculator that calculates a basic pressure that is a candidate for the target pressure based on information related to the operating state of the engine;
A limit pressure calculation unit that calculates a limit pressure that is a candidate for the target pressure based on a turbine speed that is information relating to an operating state of the turbocharger, and
The limit pressure calculation unit includes an expansion ratio data in which an expansion ratio in the turbine is defined in advance for each turbine speed, and selects the expansion ratio defined in the current turbine speed from the expansion ratio data. The limit pressure is calculated by multiplying the selected expansion ratio by the outlet pressure of the turbine. In the expansion ratio data, the higher the turbine rotation speed is within a range where the turbine rotation speed is larger than the allowable rotation speed. The expansion ratio is low,
The control unit sets the basic pressure as the target pressure when the basic pressure is equal to or lower than the limit pressure, and sets the limit pressure as the target pressure when the basic pressure is higher than the limit pressure. Type turbocharger control device. The expansion ratio data is
A reference expansion ratio associated with a reference atmospheric pressure, which is an atmospheric pressure used as a reference when selecting the expansion ratio, and a low pressure expansion ratio associated with an atmospheric pressure lower than the reference atmospheric pressure, The low-pressure expansion ratio that is a value smaller than the expansion ratio is defined in advance for each turbine speed,
The limit pressure calculator is
The control apparatus for a variable capacity turbocharger according to claim 1, wherein the expansion ratio corresponding to the turbine rotational speed and the atmospheric pressure is selected from the expansion ratio data. The expansion ratio data is composed of a plurality of data in which one expansion ratio is defined for each turbine speed.
The reference atmospheric pressure is a pressure value having a predetermined range,
The plurality of data are:
Reference data corresponding to the reference atmospheric pressure;
Low pressure data corresponding to an atmospheric pressure lower than the reference atmospheric pressure;
The variable capacity turbocharger control device according to claim 2, comprising high-pressure data corresponding to an atmospheric pressure higher than the reference atmospheric pressure. The limit pressure calculation unit is a first limit pressure calculation unit;
The limiting pressure is a first limiting pressure;
The expansion ratio data is first expansion ratio data;
The expansion ratio selected from the first expansion ratio data is a first expansion ratio;
A second limit pressure calculating unit that calculates a second limit pressure that is a candidate for the target pressure based on an intake air amount that is information relating to an operating state of the turbocharger;
The second limit pressure calculation unit is
The expansion ratio includes second expansion ratio data defined in advance for each intake air amount, and the expansion ratio defined for the current intake air amount is selected as the second expansion ratio from the second expansion ratio data. Multiplying the selected second expansion ratio by the turbine outlet pressure to calculate the second limit pressure;
The controller is
The control of the variable capacity type turbocharger according to any one of claims 1 to 3, wherein a smallest value among the basic pressure, the first limit pressure, and the second limit pressure is set as the target pressure. apparatus. The second expansion ratio data is
A second reference expansion ratio associated with a second reference atmospheric pressure, which is an atmospheric pressure used as a reference when selecting the second expansion ratio, and a second air pressure associated with an atmospheric pressure lower than the second reference atmospheric pressure. A second low-pressure expansion ratio, which is a value smaller than the second reference expansion ratio, for each intake air amount ;
The second limit pressure calculation unit is
The control apparatus for a variable displacement turbocharger according to claim 4, wherein the second expansion ratio corresponding to the intake air amount and the atmospheric pressure is selected from the second expansion ratio data.

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